Coupling device for radio purposes



June 3, 1941- w. A. SCHAPER COUPLING DEVICE FOR RADIO PURPOSES Original Filed May 18, 1936 5 Sheets-Sheet l INVENTOR. WILLIAM A SCH/IP52 BY MM @114 AfToRNEY.

June 3,- 1941. w. A. SCHAPER 2,244,025

COUPLING DEVICE FOR RADIO PURPOSES Original Filed Mayl8, 1936 5 Sheets-Sheet 2 INVENTOR. W/LL/AM A, SCHAPEQ BY O/MMJ'ZZ. M

ATTORNEY.

June 3, 1941. w sc 2,244,025

' COUPLING DEVICE FOR RADIO PURPOSES Original Filed May 18, 1936 5 Sheets-Sheet 3 INVENTOR W/LL/AMA. SCHAPE/Q BY AZMM (2; m

ATTORNEY.'

I June 3, 1941.

w. A. SCHAPER 2,244,025

COUPLING DEVICE FOR RADIO PURPOSES Original Filed May 18, 1936 5 Sheets-Sheet 4 II] t INVENTOR. W/LL/AMA 5CHAPEQ ATTORNEY.

June 3, 1941- w. A. SCHAPER 2,244,025

COUPLING DEVICE FOR RQDIO PURPOSES Original Filed May 18, 1936 5 Sheets-Sheet 5 INVENTOR.

VV/LL/A M/LSCHA PEQ ATTORNEY.

Patented June 3, 1941 UNITED STATES PATENT OFFICE COUPLING DEVICE FOR RADIO PURPOSES William A. Schaper, Cicero, lll., alaignor to Johnson Laboratories, Inc., Chicago, Ill, a col- My invention relates to intermediate-frequency coupling devices for superheterodyne radio receivers, and particularly to those of the type employing an inductance coil or coils, and a core or cores of comminuted ferromagnetic material, compressed and held in solid'formby a binder. The cores preferably are movable relatively to the coils to effect tuning, and a fixed capacitor or capacitors are provided for supplying th capacitance required to produce resonance at the desired intermediate frequency.

As is well known in the art. regardless of how carefully intermediate-frequency coupling devices may be made in the factory, and there ad- Justed to resonance at a desired frequency, such coupling devices cannot be exactly duplicated owing to practical limitations in manufacture. Furthermore, regardless of how carefully the receivers in which the coupling devices are to be used may be designed, constructed and wired to prevent it, different stages even in the same receiver differ in circuit capacitance, and receivers of different manufacture show even more marked circuit capacitance differences. It is thus always necessary for the manufacturer of such coupling devices intended for use by receiver manufacturers generally, to provide the coupling devices with suitable means for accurately tuning the coupling devices to resonance at the desired intermediate frequency, after the coupling devices have been incorporated in the receivers in which they are to be used, and the tuning means employed must have a substantial range to compensate for the circuit capacitance difl'erences Just referred to.

It is a principal object of my invention to so construct my intermediate-frequency coupling device that the electrical factors controlling selectivity and gain are maintained substantially constant throughout the tuning range of the coupling device, as below described.

This is a divisional application of my copending application Serial No. 80,233, filed May 18, 1936, now Patent No. 2,141,254, December 2'1. 1938, and is directed particularly to the coupling devices of my invention disclosed in said earlier application.

My invention will be best understood by reference to the accompanying drawings illustrating several means preferably employed, in which Fig. 1 illustrates partly in side elevation and partly in vertical, sectional view, one form of my coupling device in which the coupling is inductive,'this view being taken along the line i-i in F l- 3;

Fig. 2 is a vertical, sectional view through the casingshowninl ig.l,andshowstheinternal parts of the device of Fig. 1 in front elevation. gas :iew being taken along the line 2-2 in Fig. 3 shows in a view similar to Fig.1 another form of my coupling device in which the coupling is effected inductively, this view being taken alongthelineJ-JinFlgJ;

Fig. 4 shows in a view similar to Fig. 2 the device illustrated in Fig. 3, this view being taken along the line 4-4 in Fig. 3;

Fig. 5 shows in side elevation to an enlarged scale, a modii'ied form of core that may be used with the coupling devices illustrated;

Fig. 6 is an end view of the core shown in Fig. 5;

Fig. 7 is a schematic circuit diagram of one use of the coupling device illustrated in Figs. 1 and v Fig 8 is a schematic circuit diagram of one use of the coupling device illustrated in Figs. 3 and 4;

Fig. 9 shows in diagrammatic side elevation, a coupling device of the kind illustrated in Figs. 1 and 2, provided additionally with magnetic coupling means;

Fig. 10 is a schematic circuit diagram of one use of the coupling device illustrated in Fig. 9;

Fig. 11 shows in atic side elevation, a coupling device in which the inductance coils are severally mounted in separate enclosing housings of ferromagnetic material, the coupling between the coils being capacitive;

Fig. 12 is a schematic circuit diagram of one use of the coupling device illustrated in Fig. 11;

Fig. 13 is a schematic circuit diagram of another use of the coupling device illustrated in Figs. 1 and 2, in which capacitive coupling is employed in addition to the inductive coupling indicated in Fig. 7;

Fig. 14 shows in diagrammatic side elevation, a coupling device similar to that shown in Figs. 3 and 4, but differing from the latter in that the transfer winding of each unit of the coupling device is connected conductively with the inductance coil of the other unit of the device, instead of the arrangement in which the transfer windings are connected together in a loop conductively separate from the inductance coils of the device, as illustrated in Fig. 8;

Fig. 15 is a schematic circuit diagram of one usedof the coupling device illustrated in Fig. 14; an

1 1g. 16 is a schematic circuit diagram of one use of a modified form of the coupling device illustrated in Fig. 14, in which only one transfer winding is employed, which transfer winding is inductively related to the inductance coil 01 the unit of which it is a part, and is conductively connected with the inductance coil of the other unit of the coupling device.

Similar numerals refer throughout the several views.

In Figs, 1 and 2, I illustrate a coupling device consisting of a base plate 10, supporting spaced and internally threaded plugs H and E2 of metal or other suitable material, on which plugs tubes l3 and Hi of insulating material are respectively mounted with their axes in parallel relation. The tube i3 supports an inductance coil 55, which is preferably made in two sections, and within the tube a core iii of compressed ferromagnetic material is disposed with a free sliding fit, the core being connected with a screw it by an insulating connector which screw extends through and fits the threads in the plug ii, whereby the core it may be moved longitudinally in the coil i5 as desired, by turning screw 6 The tube it contains a, similar core its 2), similarly connected with a screw it engaging the plug 12, for cooperation with an inductance coil mounted in two sections on the tube id.

The end portions of the base plate In support fixed capacitors 2i and 22 which are connected respectively with the terminals of the coils i5 and 20. A metal shield can 23 surrounds the base plate l0 and the parts carried thereby, the base plate being supported adjacent one side wall of the shield can by nuts 24 and 25 on the externally threaded ends of the plugs II and I 2 respectively which extend through the shield can.

With the construction described, the spacing of the tubes i 3 and I4 from each other establishes the desired degree of inductive coupling between the coils l5 and 20, and the capacitances of the fixed capacitors 2i and 22 are so selected that they will tune the coils of the coupling device to the desired intermediate frequency, with the cores I6 and Mia in intermediate positions in the tubes l3 and M.

In Fig. 7, I illustrate the coupling device described, as connected between the vacuum tubes T and T1 of a circuit to constitute a high-frequency amplifying stage. The terminals of the coil 20 are connected with the terminals of the fixed capacitor 22 and by Wires 26 and 21 with the plate P of the vacuum tube T and with the positive terminal of a high-voltage source, re-

to similar parts spectively. The terminals of the coil l5 are connected with the terminals of the fixed capacitor 21 and by wires 28 and 29 with the grid G1 of the vacuum tube T1 and with ground, respectively. The cores I611 and I6 are then adjusted to tune the units of the coupling device to resonance at the desired frequency and to compensate for the electrical conditions peculiar to the particular circuit in which the coupling device is to be employed.

In permeability-tuned intermediate-frequency coupling devices as used heretofore, in which the coils are inductively coupled, the amount of coupling necessarily varies, for resonance at any particular frequency, with changes in the capacitance employed in each resonant circuit. Hence, where coupling devices of the kind under consideration are employed, and the capacitance of the tuned circuit is changed from its original value by variations in the capacitance of the wiring or other parts of the network in which it is incorporated, the inductance of the resonant circuit must be correspondingly and oppositely changed to maintain constant the value where i is the resonant frequency, and L and C are respectively the inductance and capacitance of the resonant circuit involved. This change in inductance is readily effected by adjustment of the ferromagnetic cores, and is effective so far as tuning to resonance is concerned, but any such inductance change effects a change in the mutual inductance and hence in the coupling of the inductively coupled units of the tuning device, producing corresponding changes in the selectivity and gain of the coupling device, unless means are employed to prevent the occurrence of such changes.

When the initial coupling is above optimum coupling where Xm is greater than R1R2, the coupling change will not appreciably change the gain of the coupling device, but will result in a selectivity characteristic of the coupling device having widely varying Widths.

For other conditions of initial coupling, although the inductance changes involved in tuning may not produce wide changes in selectivity, they will produce substantial changes in gain. To correct for these changes in selectivity and gain, and maintain them substantially constant, it is necessary to vary the mutual inductance of the coupling device, as well as it L/R or inductance-to-resistance ratio. This I accomplish as below described.

For a conventional intermediate-frequency coupling device, it can be shown that the selectivity is represented by the equation 1 2 2 /1 5, 5 (2 where Er is the Voltage at resonance, fr is the resonant frequency, E is any other voltage less than Er,

and BW is the band width.

But since Q= L/R and w is equal to 21rf, L is the inductance and R is the resistance of the coupling device, Equation 2 becomes 7 R z 1.41 2TL(E 1 (3) To satisfy Equation 3 for fixed values of Er and E in order to maintain a constant value of BW, that is, constant selectivity, the ratio R/L must be maintained constant.

Again, to express the gain of the coupling device, where Z1 is the impedance of the input unit of the device (for example, the coil 20, core lGa, capacitor 22 and attached wiring, Fig. '7), Z3 is the impedance of the output unit of the device (for example, the coil 15, core I6, capacitor 2| and attached wiring, Fig. 7), and Z2 is the mutual reactance of the device (for example, the mutual reactance between the coils 20 and 15, Fig. 7), for a constant voltage across Z3 which expresses the ratio of the input voltage to the output voltage of the coupling device, where Xm is the mutual reactance between the units of the coupling device, and L. C and R. are retively the inductance, capacitance and resistance oi. the output unit of the coupler. This may also be expressed for rwonant frequency as from which, to maintain a constant gain, the product of the factors Km, 0 and R/L must be maintained constant, and where the factor R/L is maintained constant, the product of Km and C must be maintained constant.

In practical operation, however, the voltage across Z1 is not a constant voltage. For example, where the capacitance of the input unit of the coupling device is increased, as it generally is when the device is installed for use, the

value or impedance of the input unit is decreased, which correspondingly decreases the voltage across Z1. To maintain a constant gain, the Km of the coupling device must be correspondingly greater than required to satisfy Equation 5. Therefore by proper choice of the mutual reactance and of the quantity L/R, substantially constant gain and selectivity may be obtained.

with the coupling device above described in connection with Figs. 1, 2 and 7, the material of the cores II and lid is so selected that the core losses will vary substantially as the inductance values as the latter are varied by movement of the cores relatively to the coils, as a result of which the effective resistance of the coil is correspondingly varied.

In. some cases, where the compensating core losses must be considerable, or where the variation of such losses must be of special kind, I find it advisable to use cores of the kind shown at It!) in Figs. 5 and 6. The core itself is made of powdered iron selected to best cooperate with the requirements of the coupling device with which the core is to be used, the iron being formed by pressure and held together by a suitable binder, and carries attached to its surface, for example, by cement, a piece of thin metal foil lie in which the high-frequency flux in the coil with which the core is used sets up eddy current losses, which add to the losses produced in the core itself. The variation of the losses in the foil lic relatively to movement of the core lib axially of the coil with which it is used may be controlled by the shape of the foil, as its width may vary in any desired manner. The core lib with its attached foil lie may be used with any of the coupling devices describedrin which it is desired to develop losses of the kind described.

A construction of coupling device having a substantially constant selectivity and amplification characteristic is illustrated in Figs. 3 and 4, in which the upper unit consists of a base plate ll, through which an internally threaded plug ll of suitable material extends to support a tube 32 of insulating material, on the outer end portion of which tube an inductance coil 33 is mounted, the coil being made preferably in two sections as indicated. Between the coil 33 and the base plate II, the tube 32 supports a coupling coil 24 consisting preferably of two separate and in sulated windings wound at the same time and constituting primary and secondary portions thereof, the coil 04 having preferably but few turns compared with coil 33. The base plate 30 supports a fixed capacitor II, the terminals of which are connected with the terminals of the serially connected coil 32 and the secondary portion of the coil 34. The tube 32 contains a core 38 of compressed ferromagnetic material secured to a screw 31- by a connecting member 8! of insulating material, the screw 21 extending through and fitting the threads in the plug 3], so that .by turning the screw in the plug, the core may be moved into and out of the coil 33. When the core is moved out of the coil 33, it is moved towards and into the coil 34, thus increasing the inductance of the coil 34 at the same time that the inductance of the coil 33 is decreased, and oppositely changing the inductances by movement of the core in the other direction.

The externally threaded end of the plug ll extends through a metal shield can 33 to receive a nut 40 by which the plug is clamped to the shield can to support the base plate near and spaced from one side wall of the shield can, with the latter containing and surrounding the base plate and the parts carried thereby.

The lower unit of the coupling device shown in Figs. 3 and 4 consists of a base plate 4|, a plug 42 and a tube 43, all of suitable material and of the same construction and purpose respectively as the base plate Ill, plug SI and tube 32 of the upper unit. The tube 43 supports an inductance coil 44 and a coupling coil 45 constructed and through the piug 42 to operate the core. The

externally threaded end portion of the plug 42' extending through the shield can, which shield can encloses the base plate 4i and the parts carried thereby. The shield can 49 is formed at its upper and closed end portion to enter and snugly fit the lower open end of the shield can 39, thereby completely shielding the upper unit of the coupling device and preventing inductive coupling between the coils 33 and 44. Coupling of the upper and lower units of the device, is eil'ected by connections between the secondary portion of the coil 45 and the primary portion of the coil 34.

As shown in Fig. 8, the coupling device illustrated in Figs. 3 and 4 has its lower or input unit connected by wires SI and 52 respectively, with the plate P of a first vacuum tube T and with the positive terminal of a high-voltage source, and the output unit of said device is connected by wires 53 and 54 respectively with the grid G1 of a second vacuum tube Ti and ground. In Fig. 8, the primary and secondary portions 45a and 45b respectively of the coupling coil 45 are shown, as are also the primary and secondary portions 340 and 341) respectively of the coupling coil 34. The secondary portion 45b is shown as connected with the primary portion 34a .by wires 55 and 56, the wire 56 preferably being grounded as indicated.

The operation of the coupling device schematically illustrated in Fig. 8 is as follows: Assuming that the capacitances of the two tuned circuits of the device are increased by its connection with the vacuum tubes T and T1, the cores 36 and 36a are slightly withdrawn from the coils 33 and 44, thereby reducing the inductance value of the coils until Equation 1 is satisfied. At the same time that these inductance values are decreased, the inductance values of the portions 45a and 34b of the coils 45 and 34 are increased, producing corresponding increases in the mutual inductances of the coils 45 and 34, which in turn has the effect of coupling circuits 34b, 33, 35 and 46, 44, 450. more closely. The inductance-to-resistance ratio is so selected that the increase in mutual inductance will maintain substantially constant selectivity and gain. The coupling between the two windings of each of the coils 34 and 45 is close which results in a nearly constant output voltage. At the same time, the increased inductances of the portions 34?) and 45a of the coils 34 and 45 respectively, result in a corresponding increase in the mutual inductance of coils 34 and 45, which increases the voltage delivered to the grid circuit of the vacuum tube T1. The coils 34 and 45 are so proportioned as to number of turns and coupling that this increase in mutual inductance compensates for the drop in voltage across the plate circuit of the vacuum tube T which is met in practice, and as a result, the gain of the coupling device is maintained at the value for which it is designed.

The coupling device diagrammatically illustrated in Fig. 9 is of substantially the same construction as that described in connection with Figs. 1, 2 and 7, the principal difference being that magnetic coupling is introduced between the units of the coupling device by means of a crossbar 51 of compressed ferromagnetic material, so positioned between the tubes l3 and 14 that its ends are closely adjacent the tubes and spaced from the lower ends of the cores (6 and 16a when the cores are in the position of maximum inductance in the coils I and 20 respectively. The air gaps between the ends of the cross member 51 and the lower ends of the cores l6 and [6a are of such length that when the cores are moved downwardly in the coils l5 and 20 by the adjusting screws l1 and 19, thereby decreasing the inductance of the coils l5 and 20 respectively, the reluctance of the common magnetic paths of the coils l5 and 20 is decreased, thereby increasing the coupling between the coils I5 and 20. This gives the coupling device illustrated in Fig. 9, more nearly constant selectivity and gain, than that of the coupling device illustrated in Figs. 1, 2 and 7, and by properly proportioning the parts and selecting the materials of the cores l6 and Mia and of cross member 51, the requirements of Equations 1 and 3 are satisfied.

Fig. illustrates schematically the connection of the coupling device shown in Fig. 9 between vacuum tubes T and T1, the terminals of the input unit of the device being connected by wires 58 and 59 respectively with the plate P of the vacuum tube T and with the positive terminal of a high-voltage source, and the terminals of the output unit of the device being connected by wires 60 and BI respectively with the grid G1 of vacuum tube T1 and ground.

In the coupling device illustrated in Fig. 11, the inductance coils 62 and 63 of the input and output units of the device are contained in shells 64 and 65, respectively, of compressed ferromagnetic material, which entirely surround the outer surfaces and ends of the coils. The shells 64 and 65 are mounted on tubes 66 and 61 respectively,

to a base plate 68 by means of plugs 69 and I0 and nuts 1| and I2 thereon. The tubes 66 and 61 contain cores l3 and 14 of compressed ferromagnetic material attached to screws 15 and 16 extending with threaded engagement through the plugs 69 and 10 respectively, so that the cores may be moved into and out of the coils 62 and 63 as desired. The terminals of the coils 62 and 63 are respectively shunted by fixed capacitors I1 and 18. The coils are coupled by means or a fixed capacitor 18 connected with one terminal of each of the coils, and the coupling is entirely capacitive since the shells 64 and 65 shield the coils and prevent appreciable inductive coupling between them.

One arrangement for use of the coupling device shown in Fig. 11 is illustrated in Fig. 12, the terminals of the input unit of the device being connected by wires 80 and 8| respectively with the plate P of vacuum tube T and with the positive terminal of a high-voltage source, and the terminals of the output unit of the device being connected by wires 82 and 83 respectively with the grid G1 of the vacuum tube T1 and ground.

The operation of the coupling device shown in Figs. 11 and 12 is generally similar to the operation of the coupling device illustrated in Figs. 1, 2 and '7. By proper selection of the material of the shells 64 and 65 and of the cores I3 and 14, the L/C ratio of each resonant circuit of the device of Figs. 11 and 12 is such that, although the capacitive coupling is fixed, as the resonant resistance L/CR of the input and output circuits of the device decreases to compensate for increased capacitance of the system into which it is connected, the voltage gain becomes greater, which compensates for the decrease in voltage across the intput unit of the coupling device which is met in practice.

In Fig. 131 illustrate a use of the coupling device described in connection with Figs. 1 and 2, which is modified only by the connection of a fixed capacitor 84 between the wires 26 and 28,

vto effect capacitive coupling in addition to the inductive coupling above described as existing between the coils 20 and I5. As far as satisfying Equations 1 and 3 is concerned, the operation of the device shown in Fig. 13 is substantially the which are of insulating material and are secured same as the operation of the device shown in Fig. 7. The added capacitive coupling afforded by the fixed capacitor 84, however, tends to estab lish a voltage in the output circuit l5--2I which will, in conjunction with the voltage established across the coil [5 due to current in coil 20, give an increased or decreased potential between the grid G1 and ground, depending on the value of the inductances of the coils 20 and 15, as well as on the mutual inductance between them. The critical point at which this occurs can be changed as desired, and as a result a characteristic of desired kind may be secured, either rising or falling or remaining constant as the impedance of the input unit decreases.

The coupling device illustrated in Fig. 14 is similar to that above described in connection with Figs. 3, 4 and 8, the difference being that the coupling coils 34 and 45 are replaced by singlelayer coupling coils 85 and 86 mounted respectively on the tubes 32 and 43. With this construction, the coupling coil 86 of the input unit of the coupling device is serially connected in circuit with the inductance coil 33 of the output unit of the device by a wire 81, and the coupling coil 85 of the output unit of the device is serially connected in circuit with the inductance coil 44 of the input unit of the device by a wire 88. As a result the coupling is inductive as to the relation between each of the coupling coils and the inductance coil of the same unit, and conductive between the units of the coupler. The coupler illustrated in Fig. 14 isshown schematically in use in Fig. 15, in which the terminals of the serially connected coils and 88 are connected by wires 88 and 88 respectively with the plate P of vacuum tube T and with the positive terminal of a high-voltage source, and the terminals of the serially connected coils I3 and 88 are connected by wires 8! and 82 respectively with the grid G1 of vacuum tube T1 and ground.

conductively and directly to the inductance coil* -of the other unit of the coupling device, instead of being so transferred, by a second inductive link as illustrated in Fig. 8. The coupling device shown in Figs. 14 and operates, therefore, somewhat more efliciently than does the coupling device illustrated in Figs. 3, 4 and 8; by properly proportioning the parts, the selectivity and gain of the coupling device of Figs. 14 and 15 may be maintained substantially constant in the manner described for the coupling device illustrated in Figs. 3, 4 and 8. a

The coupling device illustrated schematically in Fig. 16 is a modification of the coupling device illustrated in Figs. 14 and 15, in that a single link circuit between the units of the coupling device is employed, instead of two such link circuits as illustrated in Fig. 15, the coupling coil I! being omitted, and the coil 44 being connected directly with the positive terminal of the highvoltage source by a wire 88. The operation of the coupling device illustrated in Fig. 16 is substantlally the same as that described in connection with Figs. 14 and 15.

From the above it will appear that by my invention I provide for maintaining substantially constant the selectivity and gain of permeabilitytuned intermediate-frequency coupling devicesduring the adjustment which may be required to tune the coupling devices to a fixed predetermined intermediate frequency in spite of elec- ,trical inequalities in the receivers in which the coupling devices are intended to be used. My invention may be embodied in different types of such coupling devices, depending upon the requirements of different cases. In applications in which the required tuning range of the coupling device can be maintained within relatively narrow limits, the coupling device may be of comparatively simple and inexpensive construction, but where substantially uniform gain and selectivity over a relatively wide tuning range is required, it may be necessary to employ one of the somewhat more elaborate types of coupling devices herein disclosed. For example, the construction of the coupling device illustrated in Figs. 3, 4 and 8 is well adapted to general use in radio receivers having widely different electrical variations, and with such coupling devices there is no need to particularly design the coupling device for any particular use, except that the particular intermediate frequency to be employed must be included within the range of frequencies which the coupling device is designed to cover.

In its broad aspect, therefore, my invention consists of providing means in a permeabilitytuned intermediate-frequency coupling device by which, on changing the inductance of the coupling device to compensate for electrical diflerences incident to its use, electrical factors of the coupling device will be automatically changed to maintain substantially constant both the selectivity and the gain of the coupling device.

While I have shown my invention in the particular embodiments above described, it will be understood that I do not-limit myself thereto, as 1'. may employ uii'alents known to the art of the various devices employed without departing from the scope of the appended claims.

Having thus described my invention, what I claim is:

1. A radio frequency coupling device, including the combination of mounting means, two spaced insulating tubes supported by said mounting mean in substantially parallel relation, an inductance coil carried by each of said tubes, a magnetic core in each of said tubes and adjustable axially therein to change the inductance of coupling coil and the inductance coil mounted therewith being spaced from each other on their said insulating tube, and the corresponding core being arranged to simultaneously move away from one of said coils and towards the other of said coils, thereby increasing the inductance of one of said coils at the same time that the in ductance of the other coil is decreased.

2. A radio frequency coupling device, including the combination of mounting means, two spaced insulating tubes supported by said mounting means in substantiallyi-parzillel relation, an inductance coil carried *byge'ach of said tubes, a magnetic core in each-of :s'aid tubesand adjustable axially therein'to change the inductance of the corresponding coil,-Ian adjusting rod connected with each ofsaid cores and extending from the corresponding tube, said coils being coupled for energy transfer from one to the other thereof, a coupling coil on each of said tubes, and means coupling each of said coupling coils with the inductance coil on the other of said tubes, each of said coupling coils and the inductance coilmounted therewith being spaced from each other on their said insulating tube, and the corresponding core being arranged to simultaneously move away from one of said coils and towards theother of said coils, thereby increasing the inductance of one of said coils at the same time that the inductance of the other coil is decreased.

3. A radio frequency coupling device, including the combination of mounting means, two spaced insulating tubes supported by said mounting means in substantially parallel relation, an inductance coil carried by each of said tubes, a magnetic core in each of said tubes and adjustable axially therein to change the inductance of the corresponding coil, an adjusting rod connected with each of said cores and extending from the corresponding tube, said coils being coupled for energy transfer from one to the other thereof, a coupling coil on one of said tubes, said coupling coil being coupled with the inductance 0011 on the other of said tubes, said, coupling coil and the inductance coil mounted therewith being spaced from each other on their said insulating tube, and the corresponding core being arranged to simultaneously move away from one of said coils and towards the other 01' said coils, thereby increasing the inductance of one of said coils at the same time that the inductance of the other coil is decreased.

4. A radio frequency coupling device, including the combination of mounting means, two spaced insulating tubes supported by said mounting means in substantially parallel relation, an inductance coil carried by each of said tubes, a magnetic core in each of said tubes and adjustable axially therein to change the inductance of the corresponding coil, an adjusting rod connected with each of said cores and extending from the corresponding tube, said coils being coupled for energy transfer from one to the other thereof, a coupling coil on each 0! said tubes, each of said coupling coils being coupled with the inductance coil on the other of said tubes, each of said coupling coils and the inductance coil mounted therewith being spaced from each other on their said insulating tube, and the corresponding core being arranged to simultaneously move away from one of said coils and towards the other of said coils, thereby increasing the inductance of one oi said coils at the same time that the inductance of the other coil is decreased.

WILLIAM A. SCHAPER. 

